Blood Pressure
Print This Post
How is Blood Pressure Measured?
19. The blood pressure has been traditionally measured with an instrument called “sphygmomanometer” in millimeter height of mercury rise (mmHg). Blood pressure is the result of two forces; (i) force from the heart as it beats and pumps blood into the arteries and throughout the circulatory system and (ii) the force of the arteries as they resist blood flow between heart beats when the heart is at rest. Thus during each heart beat, the heart muscle contracts to push blood around the body. The pressure produced by the heart is the highest when it contracts to push the blood on its journey through the body and this is known as “systolic” (higher value) pressure and indicates the activity of the heart. Then the heart muscle relaxes before its next contraction, and the pressure is at its lowest, which is known as “diastolic” (lower volume) pressure and shows the condition of blood vessels.
20. Both systolic and diastolic pressures are measured when you have your BP checked. For example, universally recognised normal BP of 120/80 represents 120 mmHg of systolic pressure and 80 mmHg of diastolic pressure. Systolic pressure range can be from 80 to 300 and diastolic from 60 to 140.
Fluctuations in Blood Pressure
21. Everyone’s BP is immensely variable during the day and night. There are many factors which can cause fluctuations in blood pressure: –
(i) Time to Time – BP readings can vary from time to time and therefore go for the average of 3 or 4 readings rather than the occasional extreme. A full bladder causes an increase in BP, so go to the bathroom first before taking a reading.
(ii) Right and Left Arm – BP readings in the right and left arm vary between them by about 10 mmHg or more. Use the arm with the higher reading to determine your diagnosis.
(iii) Age – Hypertension is more common with advancing age, particularly in populations, who have a high salt intake, so age must be taken into account when considering the prevalence of hypertension.
(iv) Stress – Your BP may go up if you are feeling anxious or stressed; e.g. when you go to see a doctor or to a hospital, you may have a temporary rise in BP which is known as “white coat” hypertension.
(v) Activity – BP is usually higher during activity or exercise and is lower when resting and sleeping. During exercise, the heart needs to pump blood around the body faster which raises the BP. Although people who exercise regularly will tend to have lower BP when at rest than non-active people.
